smart card

Any plastic card (like a credit card) with an embedded
integrated circuit for storing information.

Smart cards are being incorporated into soldier's dog-tags and
used to store hospital patients' medical records. This way
they are always instantly accessible.

Other uses are as a form of token in banking systems. You
could store electronic money on the card or less valuable
tokens such as those given away by petrol companies which you
collect to exchange for free gifts at a later date. The idea
being that one smart card is easier to carry around than a
multitude of paper tokens.